AB0764 EVALUATION OF THE APPLICABILITY OF THE 2022 AMERICAN COLLEGE OF RHEUMATOLOGY-EUROPEAN ALLIANCE OF ASSOCIATIONS FOR RHEUMATOLOGY CLASSIFICATION CRITERIA FOR ANTINEUTROPHIL CYTOPLASMIC ANTIBODY-ASSOCIATED VASCULITIS TO AN ASIAN POPULATION
Authors: R. Kuwata, Y. Shirota, T. Shirai, H. Yamashita, H. Sato, T. Takeda, Y. Oka, T. Kobayashi, K. Motomura, T. Kodera, H. Kaneko, J. Kameoka, H. Fujii, T. Ishii
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> The 2012 Chapel Hill Consensus Conference (CHCC) definitions and the 2007 European Medicines Agency (EMA) algorithm have been commonly used for the diagnosis of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) as a conventional and reliable method. Recently the 2022 American College of Rheumatology (ACR)-European Alliance of Associations for Rheumatology (EULAR) classification criteria for AAV have been released. It is well-known that patients with granulomatosis with polyangiitis (GPA) are predominantly proteinase 3 (PR3)-ANCA-positive in the U.S. and Europe, but myeloperoxidase (MPO)-ANCA-positive patients with GPA are more prevalent in Japan. However, very few studies have been available on the evaluation of the applicability of the new criteria to an Asian population. <h3>Objectives</h3> This study aimed to assess the applicability of the 2022 ACR/EULAR classification criteria to AAV patients from an Asian background. <h3>Methods</h3> This study included a total of 415 patients (mean age = 64.2 years, standard deviation [SD] = 16.3 years) diagnosed with AAV by the conventional method at three medical institutions in Japan between 2000 and 2022. Only Asians accounted for the whole population comprising 139, 128, and 148 patients (mean age = 65.2 years, SD = 15.7 years; mean age = 70.8 years, SD = 13.8 years; mean age = 56.1 years, SD = 15.8 years) diagnosed with eosinophilic granulomatosis with polyangiitis (EGPA), GPA, and microscopic polyangiitis (MPA) by the conventional method, respectively. The applicability of the new criteria to AAV patients in Japan was assessed through the verification of the consistency with the conventional diagnoses. Additionally, phenotypes of organ involvement were analyzed in each reclassified group from the conventionally-diagnosed GPA population. <h3>Results</h3> The patients diagnosed with EGPA and MPA by the conventional method were significantly more likely to be reclassified into the same AAV subphenotype (138 out of 139 patients [99.3%] and 145 out of 148 patients [98.0%], respectively). On the other hand, the patients diagnosed with GPA by the conventional method were less likely to be reclassified into the same AAV subphenotype (91 out of 128 patients [71.1%]). In the conventionally-diagnosed GPA population, 71 patients were reclassified as GPA, not as MPA, 20 were reclassified not only as GPA but also as MPA, and 36 were reclassified not as GPA but rather as MPA. In the group reclassified only as GPA, there were 59 patients with sinusitis, including ten patients with orbital mass lesions. In the group reclassified both as GPA and as MPA, there were 20 patients with severe organ involvement, including 15 patients with pauci-immune glomerulonephritis (PIGN). <h3>Conclusion</h3> The new criteria gave more weight to ANCA serology than histology and surrogate markers compared with the conventional method, which kept diagnostic consistency in the conventionally-diagnosed EGPA and MPA populations. At the same time, the new criteria occasionally led to a big diagnostic contradiction in the conventionally-diagnosed GPA population from an Asian background. In the conventionally-diagnosed GPA population, the new criteria were likely to reclassify MPO-ANCA-positive patients as MPA. However, it is noteworthy that the new criteria were still beneficial in extracting GPA patients with recurrent or severe organ involvement, including orbital masses and PIGN. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.